You pretty much have to run MYOB in a VM, or possibly via WINE. I keep an older windows laptop around at work for MYOB duties. As far as I know there are no alternatives that have anything near the feature set, or the integration with the ATO and other services that MYOB offers.
These days with it all being cloud based there is some web browser based functionality but in it's current state it is much more limited than it should be.